Giner, Inc. proposes a portable, inexpensive, and rapid-response monitor for arsenic speciation in urine. Arsenic species excreted in urine are reflective of exposure to toxic arsenic species, and therefore this monitor will be a valuable tool in medical diagnostics and epidemiological studies by allowing determination of arsenic exposure by a technique that is faster and less expensive than traditional methods. Improved capability of monitoring exposure will have positive public health outcomes, as long- term exposure to arsenic is associated with health problems including cancer and cardiovascular disease. The phase I program developed a sensor capable of electrochemical detection of arsenic (III), total inorganic arsenic, and dimethylarsenic acid. Total organic arsenic was determined through a sample treatment process followed by electrochemical detection. The phase II program will include further optimization of all methods and processes, design of a prototype device, and validation of the device with real urine samples from epidemiological studies. The phase II program will result in a practical, robust, and accurate arsenic speciation device.